bomberbaz

Thanks dave, didn’t actually take that fully into account. Given I have no idea about the focus point of a H20 0.965 vs a 1.25 zoom I will hold off. I do know someone who can help in this matter though, cheers.

I have an novice acquaintance who has a decent tasco 115/900 reflector which is EQ mounted. The tripod is reasonably solid. The mount head has a badly worn gear in RA in one spot only. So I removed the counterweight and bar then set the mount to work in alt-az. Seems quite solid and functional in this mode plus is much easier to use for a complete novice. Anyway, happy enough with that part given it was a well meant gift from his swmbo. Suggesting a brand new setup wasn't really an option. The issue is It is fitted for older 0.95 eyepieces and after discussing options he doesn't want to go to the bother of the replacement focuser. I am thinking a 1.25 adaptor with a zoom would work well. My understanding is that using a 8-24 zoom with the relatively narrow fov will minimise any vignetting, thoughts? Also is there anything else i am over looking. Cheers all Steve

Just added a little more data to this and reprocessed. I tried to get a more eroded star image and be less aggressive on getting the nebula to show. I like this new one, looks more natural than the august one at the top. The top image was done back in mid august, the other new image is from today.

I bought the APM 24 mentioned in this thread off the back of something you put into another thread I wrote some while back, it framed IC434 / HH perfectly in my scope with a shade under 1 degree FOV.

haha, very droll Jeremy

There has been a lot of information around around the use of visual filters, some people like to use them, some people not so and I fall into the former camp. It depends what you are viewing, scope size has a bearing and some objects are pretty much invisible without a filter. So I decided to stoke the filter fire a little myself by carrying out some of my own research. The equipment used is my Taurus 14" with DSC, a range of fixed focal length and zoom eyepieces and filters used are Astronomik. I made good use of my observing hood, I never really appreciated the benefit of a hood until I got one 18 months or so since. Being able to relax your eyes and get to the eyepiece in absolute dark is something all astronomers should experience and it sits in my bits n bobs bag which accompanies me to every nights observing. (Unlike my observing chair) These findings are all kind of personal but I believe certain aspects are more universal such as exit pupil to sky brightness correlation as an example. More on this later. I know of information going around regarding rules of thumb or theories for filters, when to use them, what type of eyepiece to use with them and on what object to use them as well. I wanted to see if some of these hold water or are simply off the cuff ways of making your opinion known and/or closing a discussion. So my main concern that i wasn't getting the best out of my equipment (no changing room jokes please) but in particular with regard to nebula viewing. After my most recent trip to Galloway (visit B ) in Bortle 2 skies I was reviewing some of my findings, comparing with my previous visit A about 4 years previous and found that for all my planning, I had neglected my exit pupil size planning for OIII sensitive nebula. In visit B I had simply used my Nikon 17mm, more for the lovely wide FOV and completely overlooked exit pupil. The Nikon gives me 3.5mm exit pupil which I personally think is the lower end size for use in more light polluted skies, certainly not Bortle 2. Previously during visit A to Galloway I had used a smaller dob, larger 22mm eyepiece with an exit pupil of 4.8mm. My previous notes (from visit A) showed some objects viewed had been a better resolved than from my visit B which made me think and it was this that prompted me to look into filters in more depth. I do think that all visual astronomy is more complicated than at first people think. In particular viewing nebula which adds an extra layer of complication to this aspect of astronomy as you are throwing another layer into the mix, namely a filter. For those who are unsure as to what I am driving at the brightness of a nebula and thus the ability to see it via a filter has many variables but given a scenario where certain aspects are equal. And we all use say and 12" dob and a identical 8-24 zoom there are limited variables. These are sky quality/location, quality of your filter, magnification/exit pupil (these are directly correlated) and finally experience. The latter is a big thing as I recently proved to myself for the umpteenth time but that's another story. Primarily i am focusing on the third variable, magnification/exit pupil but this does bring into it the quality of filter variable. Anyway, my last few trips out I have been experimenting with different exit pupil sizes for line filters (OIII/HB) and to a lesser extent, UHC narrowband. I am not going to go through every single test or object but in broad terms I selected all emission type nebula with a mix of diffuse & planetary. I didn't bother with reflection type objects as these tend to behave differently. I did lean towards more faint nebula because a lot of planetary are seen relatively easy due to their size and relative high surface brightness. I tested out at three sites of varying darkness (SQM 20.25-21.15). My HB/OIII system was to start with a 24mm APM (It's my goto line filter) and vary between other ranges from 17mm to 28mm. The exit pupil range goes from 3.5mm to 5.8mm. (magnification variance 100-61) For UHC I varied all the way from 5.8 to 1.6mm exit pupils. That's 28 to 8mm eyepiece or mag 61-214 😱 My finding at all sites were identical but in the darkest skies, the results were slightly less conclusive for line filters HB filter targets were a mix of sharpless, NGC and IC catalogue. Performance at exit pupil size of lower than 4mm (baader zoom at 20mm) had a low responsiveness of nebula. I saw very little at these low exit pupil sizes and given the low actual brightness of these objects in general and tight bandpass of HB it is not surprising to me to find this. I did manage a very feint NGC 1499 and campbell's H star but nothing else verified. The most responsive eyepiece in my scope was the 24mm APM UFF which gave a 4.9mm Ex pupil. On campbell's H star I found a slightly larger exit pupil may have been an advantage but this was inconclusive. I would also point out that this Ep (24mm apm) and filter combination gave me my only successful view of the horsehead nebula. I had a similar result with my OIII filter, however at the darkest sites I found that a 26mm eyepiece might have offered slightly more than the 24mm, it was hard to tell, possibly equal view at times, on occasion I simply called it a draw. To be fair the 26mm eyepiece didn't help as the eye relief was awful so I simply gave up trying and called it a draw. For information purposes the 26mm gives a 5.35mm exit pupil vs the 4.9mm. A difference in area of light collected of 15% so something to think about for me here. Staying on the OIII I did find it more responsive to higher magnification/lower exit pupil than the HB although at my good to very good skies where tests took place the benefit of this were less on diffuse objects than on brighter planetary. Pushing the magnification on diffuse nebula (EG Pacman) allowed me to tease out a little better detail in the brighter areas but the overall image was less resolved than at lower magnification/larger exit pupil. For comparison purposes the 17mm Nikon gives an exit pupil that is nearly 60% less in area than a 24mm eyepiece. (0.243 vs 0.096 sq cm) Regarding UHC. I did, if I am honest become too pre-occupied with line filter testing and only did limited testing on this filter class. I find that UHC and OIII are more closely aligned than UHC/HB filters. I don't know what the full technicalities of this are other than I find OIII seems to be greater light emitting than HB. UHC filters have the greatest range of variation of exit pupil response, have the greatest overall range of responsive objects (arguably) of the three filters and certainly should be the first filter you buy if you're on a limited budget. I can happily pop the UHC/zoom combination and take it up to x140 on planetary. Beyond this and no filter vs filter becomes the question, I am then pushing the exit pupil below 2mm, the skies are pitch black and many nebula readily pop into view anyway without a filter. Even on diffuse nebula (of which I only did a couple) I was able to push it to the same x140 but the benefit was limited, if any and I doubt I would make a habit of doing this. I think optimum for UHC is much more varied, ranging an exit pupil anything from 3.5-6mm (at dark skies) with the ability to still be effective all the way down to 2mm. As mentioned beyond this your maybe as well without a filter. When you compare a nebula viewed via a UHC against a line filter your liable to find two major differences, the UHC will probably be brighter but the line filter will yield more detail due to it's much narrower bandpass. I found the nebula that fits this comparable best was the crescent (NGC6888). Very bright and apparent viewed in UHC and easy to observe, notably darker in OIII but the detail was superb, much more of a 3D effect at the expense of brightness. For the record the OIII view easily wins imho. Based upon these results my possible search for another eyepiece for OIII has been shelved. If I can pick up the right EP at 26mm I might bite but I am in no rush. I did make a post querying a 20mm EP as a potential suitor for this position some time back, I am glad I didn't bite before looking into this matter more closely. The HB filters long used rule of thumb 5mm exit pupil seems to hold true to me. This is the rule that a 5mm exit pupil holds the perfect combination of line reduced light and what hits the retina. (think that's right) Anyway, it was this rule that helped me bag the Horsehead last year The fact OIII seems to have the same was not unsurprising although my caveat ref 26mm possibly being better in ultra dark skies is interesting and something I will look into when opportunity arises. The above is very subjective because my eyes are not the same as yours, your equipment is not the same as mine and so results may vary. Other research (reading webpages from various sources mainly) I have carried out suggests that filters used under light polluted conditions should have a smaller exit pupil/more magnification to darken the skies more to improve the contrast. I do know this works but I also know from experience that under severe light pollution (like my garden), you should simply stick to planets or other bright objects and save your filters for darker skies. The darker, the better I feel I still have unsolved questions regarding both OIII and HB. But for now I am happy that my current set of available tools as it were are up to the job in hand.

I could have kicked myself I was so annoyed as this was the second time out I had forgotten my seat. I had even written on the bottom of my observing notes, "Don't forget seat" in bold type, fgs. 🙄 My observing site is just off the side of the road very near the stone circle. I was looking at the stone circle area as the southern aspect is more level, next time I go up there I will arrive a bit earlier to see if there is a second spot I can try out. 👌

Sorry my bad, I thought I read different, sorry for confusion. ZWO ASI 120MM Mini USB 2.0 Mono Camera | First Light Optics £149, best thing is it's very lightweight

Yes a cracking report, seems you had a similar experience to myself albeit with a different range of equipment. You mention the baader has a narrower bandpass, according to my findings they may be too narrow. The Baader filter seems to cut out most of the secondary 495.9 wavelength, the result will be to reduce both brightness and contrast. SearchLight Spectra Viewer from Semrock As like me you enjoy your nebula, I have always found this to be a useful guide. Filter Performance Comparisons - Astronomical Filters - Articles - Articles - Cloudy Nights cheers steve

The title sums it up as briefly as possible, but let me put some more meat on the bones. I found, using a combination of the light pollution map and google maps/earth what I hoped to be a superb dark sky site. Great I hear you say, but (there is always a but) this site was 100 miles and nearly 2 hours drive away in Keswick. Unperturbed by this I decided to give it a go last night, no moon to speak of and forcast clear skies. So packing my TS350 dob, two boxes of glass and a variety of other bits and bobs into the boot of the car and set off. 45 minutes in up the M6 I realised I had forgotten my observing seat yet again, gahhhhhhh 🤬 I managed a workaround to that seat issue using my manfrotto, a picture of this can be seen below. Not the most comfortable but I made use of it a few times. 🤣 Marks for ingenuity? To the nitty gritty. After setting up well before dark I was concerned that the sky was very cloudy and not at all what clear outside forecasted. My concern (and most of the clouds) evaporated just before dark as it all just suddenly cleared and left me with dark and beautifully starred skies above. See picture below, just a 30 second snap with a small stretch. So one of my aims was to test out exit pupils on HB and OIII filters. I tried out both the filters on many different nebulae of differing type, emissions and make up and to cut it all short, the 24mm APM with an exit pupil of 4.9mm was for me the most consistant performer. Rather ironic given all my work as it was bought as a HB filter in the first place 🙄It provided the most contrast, definition and brightness of the eyepieces used. (Exit pupil variance from 3.5 to 5.8mm) Back to the venue, it was selected based upon it having a good allround darkness and specifically a dark southern horizon. The bush in the picture above is due south, remember that picture is 30 seconds at ISO 800 and is stretched, it was super dark in comparison to my previous dark site used. My second DSO of the night showed just how good the horizon was, I went to M17 Omega/Swan nebula using the APM 24 as the opening eyepiece armed with an astronomik OIII filter and "wow", I mean "WOW". This is without a shadow of a doubt the best view of the Swan I have seen by a country mile. The shape, structure and strength of the nebula itself was quite sublime, it gave an almost 3D effect though the depth and variance of the nebula combined with the structure within, the wings were absolutely gorgeous, you get the picture. (This is at 15 degrees on the horizon) Now this was a very difficult object to view as it was, as mentioned so low and even with the boot stool, my back was going crazy but I did find it so very hard to pull myself away from it, it was simply stunning! I had similar superb results on the whole veil, it just jumped out at you, the crescent was popping readily into view showing a fully joined image, again with good structure around the inner area, the pacman and bubble nebula were firsts at this venue with the former providing the most detail/structure and firsts again for heart and soul nebula. The last two weren't brilliant but I got them as it were. With the HB my previous venue gave blanks on all but Campbell's hydrogen star & california. Last night I added to that with first sightings of gamma cygni, the cocoon and Sharpless2-91 & 101. None of the four firsts were much to write home about, mainly fuzzing or hazing of the sky although gamma cygni gave a feint amount of structure by running the FOV slowly over the area of nebulosity. Other viewing were M31, 33, 101, 102, 81, 82, 51. All of these were excellent objects to behold in these lovely dark skies. I was using the Baader 8-24 to zoom in and out to find the best strength to apply to them. x140 seems to be the sweet spot for galaxies using the dob although I went as high as x215 and although I loved the ubiquitous zoom, I missed having the extra FOV that my Nikon gives me when viewing galaxy DSO. I viewed a few other clusters and doubles, again the zoom excels here (Albireo was a peach) and I have one final object to report on with a question. I spent a while viewing M57 the ring, I was cranked right in at x215 (no filter) and I am sure I could see a greenish bluish tinge to the nebula. Am I imagining this or has anyone else seen this? In summary an excellent site that has only been excelled by my visits to Galloway. An overall 9 out of 10 for darkness that produced an SQM reading of 21.15 and likewise a 9/10 for an excellent southern horizon, the one area I have constantly struggled with. Down side distance but of course you get out of this hobby what you put into it. I will be back for a couple of goes over the winter viewing during galaxy season where I think it will really excel. Going forward my 25 minute drive (SQM 20.5 ish) site with an average southern aspect will remain my chosen site for the bulk of my viewing. I have enjoyed writing this review as I was reliving my exploits of last night whilst doing so. thanks for reading. Steve

My two penneth worth: I started out imaging because of the AZ Gti EQ capability when paired with the ASI Air Plus (£320 new). I didn't want weight or faff, the Air+ is a game changer as far as imaging goes, polar alignment is easy peasy and the combo of the Gti and air+ meets my requirements perfectly. (I can pick the whole rig up one handed) It (the air+) is compatible with your canons, so no need for a new camera, think it is also compatible with your guide so the only thing extra you need is a guide scope. ( Astro Essentials 30mm f/4 Mini Guide Scope | First Light Optics ) £59 quid new and a cable or 2 maybe. I realise it is all extra expenditure but you will get the best out of your existing kit, with the right new bit of kit. One other thing which I am sure you are aware of is weight. Your setup would be touching AZ Gti limits, maybe even slightly over so good balancing is a must. (As mentioned you will need a counter balance bar and 2kg of weight for the PDS) Steve

Some zoom eyepiece porn here 😅 APM Telescopes. Zoom Eyepieces (apm-telescopes.net)

excellent work, a quick comparison to the JWST image (you were expecting this no doubt) shows you have captured quite a few of the smaller background galaxies in Stephan's Quintet. A resounding success given your skies and equipment. 👌

well diameter is 60mm and yes the bolt does push up to engage with whatever you put on top. Pushes up by circa 10mm

Top of mine

The bumf on Flo's page states it is a 1.75 tripod, if that be the case the answer should be yes. Caveat, some of these tripods have a metal locking protusion that engages with the mount and this might be the same. I will put a picture up of mine later, mine works with it. Sky-Watcher HEQ5 PRO Go-To Astronomy Mount | First Light Optics

another sterling effort Lee, nice work indeed. BTW it's not that noisy pal, your just over self critical.

Coincidentally I saw this on Thursday, well the part below in the inner circle. I was using my 14" DOB, an Astronomik OIII filter and switching between a APM 24mm and 26 Plossl for different exit pupils in B4 skies. It's quite distinctive but my problem is it is so big you can lose perspective as I simply can't fit enough of it into a full FOV. Both EP above give less than a degree. Anyway, it is to my eyes not distinct in edge definition but there is good structure within it if that makes sense. I moved the FOV in and out of the nebulosity and it is relatively easy to pick it out doing so.

Last night I set out on something of a mammoth observing session so decided early on to leave planetary until after the faint DSO to save ruining my dark adaptation. In the end I struggled because Saturn being lowish was a royal PITA to view without an observing chair, (yes I forgot the blooming thing again) and my back was playing hell with me stooping over. So my time was limited to around 15 minutes overall but after trying magnification ranging from x 210 all the way up to x560 using the Nagler zoom, I actually settled on the x 210. This was mainly down to comfort and control factor, sat down I would have been able to control the DOB better and I could then have managed the higher settings easier. The skies were excellent btw, very settled. So didn't get the Cassini division, hints of it but to be honest I was concentrating on it's moons. In the end I managed Titan of course, along with Iapetus, Rhea and Dione. I think Enceladus was there too but as always with it being so close to the planet itself, the glow off the planet drowned out the moons a little. One thing I intend doing next time, slightly annoyed I never thought about it last night was to try out using the ND filter to calm it all down a little. Guessing with that Cassini would have been easy too last night. I did spend a few minutes right at the end on Jupiter but it was late by then. Next time I will have a go at the two outlying gas giants as well. Anyway, for 15 minutes a productive little Saturn session and a teaser of things to come i hope as I expect there to be other clear nights this next week when I will remember my chair.

That is beautiful, looks like a water fountain gently spraying before falling back. Nice work michael.

Best of all Lee, very simple (as well as effective).

Not sure Lee, that is kinda what I mean. See a more detailed sketch below to illustrate.

I didn't replce it Lee, just added an extra one as mentioned above. Refer to the small red arrow in my first picture. The spring pushes against the casing and motor housing as oppose to pulling like the installed one does.

TBH I have never found the need to put mine onto my steel tripod and simply keep the smaller SW tripod permanently set up. I do agree that in terms of stability it is an improvement but how significant that is is arguable. I have been meaning to put details of my minor mods up so here goes. I placed a small but fat spring between the outer casing and the drive motor (see red arrow). When this is fastened up is stops the slop in RA as the small spring installed is simply too weak. I also slipped two small pieces of plastic (I sabotaged a teflon type chopping mat) and slid them between the motor housing casing and the actual drive mechanism housing. (see yellow arrow) This helps take out a little of the slack in RA too. Since I did this with the new mount, my tracking has tightened up significantly and is always under 1 and I guess is averaging at 0.8. (previously circa 1.2) If anyone needs pictures, let me know. Steve

I love these deep field images, especially when you can pop in a well known character with it. How far is the most distant of these if you know that is Dan?